Apparatus for enlarging well bores



Oct. 4, 1955 A. w. KAMMERER 2,719,700

APPARATUS FOR ENLARGING WELL. BOREIS Filed May 7, 195] 2 Sheets-Sheet l I' B 1: f9, 21g?! I l 14 Q 1%"; 5 r 12 m a} .2 2 50 I fi ARCHER m mun/1mm, 26 A 29 A. 226 INVENTOR.

25 ma 2? BY A T TORNEV- Oct. 4, 1955 w. KAMMERER I 21,719,700

APPARATUS FOR ENLARGING WELL BORES Filed May 7, 1951 2 Sheets-Sheet 2 A T TORNEK United States Patent" APPARATUS FOR ENLARGING WELL BORES Archer W. Kammerer, Fullerton, Califi, assignor, by direct and mesne assignments, to Rotary Oil Tool Company, Huntington Park, Califi, a corporation of California Application May 7, 1951, Serial No. 225,005

16 Claims. (Cl. 25576) The present invention relates to rotary drill bits, and more particularly to drill bits of the type having expandible cutters for drilling a hole below well casing larger in diameter than the inside diameter of the casing through which the bits must pass.

In my application for Multiple Expansion Rotary Drill Bits, filed August 18, 1950, Serial No. 180,167, now Patent No. 2,650,072, an expansible type of rotary drill bit is illustrated for greatly enlarging the diameter of well bores through use of a plurality of cutters, which individually operate upon different portions of a formation shoulder in the well bore.

An object of the present invention is to provide an expansible drill bit having cutters that are expandible to different lateral extents from their retractedpositions, for the purpose of operating simultaneously upon different portions of the bore hole formation, and in which the drill bit is more stable and has a greater tendency to drill a concentric hole.

Another object of the invention is to provide a drill bit of the expandible type having cutters individually operating upon different portions of a formation shoulder, in which the formation itself is caused to act upon the cutters; so as to stabilize them during their revolution in the hole, causing the cutters to mutually support one another and to trace paths on the formation shoulder concentric of the hole axis.

A further object of the invention is to provide a rotary drill bit of the expandible type having cutters that collectively form a stepped shoulder in the well bore, which shoulder coacts with the cutters to stabilize the drill bit and minimize the shock loads to which it would otherwise be subjected.

Yet another object of the invention is to provide a rotary drill bit having expandible cutters that are so disposed with respect to each other as to permit the use of larger cutters which may yet be fully retracted within the body of the drill bit.

Still a further object of the invention is to provide an improved spring seat arrangement in an expansible drill bit which facilitates assembly of the bit parts.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of a form in which it may be embodied. This form is shown in the drawings accompanying and forming part of the present specification. It will now be described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

Figure 1 is a side elevation of an expansible rotary drill bit embodying the present invention;

Fig. 2 is a cross-section, on an enlarged scale, taken generally along the line 22 on Fig. 1;

Fig. 3 is a longitudinal section through the drill bit,

2,719,700 l atented Oct. 4, 1955 taken along the line 3-3 on Fig. 2, with the cutters in retracted position;

Fig. 4 is a view similar to Fig. 3, illustrating several of the cutters in their outwardly expanded positions;

Fig. 5 is a somewhat diagrammatic view illustrating the different extents of expansion of the cutters, and their manner of forming and operating upon a stepped formation shoulder, which they produce in the well bore;

Fig. 6 is a cross-section taken along the line 66 on Fig. 3;

Fig. 7 is a somewhat diagrammatic view looking upwardly from beneath the drill bit, disclosing the different paths traced on the formation shoulder by the cutters when in expanded positions;

Fig. 8 is a cross-section taken along the line 8-8 on Fig. 3.

The drill bit A disclosed in the drawings may be attached to the lower end of a string of drill pipe B, by means of which the bit can be lowered througha well casing (not shown), for the purpose of greatly enlarging the well bore below the casing shoe (not shown). The drill bit cutters 10, 10a, 10b are expanded outwardly to different extents, for the purpose of producing a stepped annular formation shoulder C in the well bore, the cutters operating upon different annular portions R, S, T of this shoulder, for the purpose of collectively enlarging the diameter of the well bore to the desired extent.

The drill bit A includes an elongate main body 11, in which a tubular member 12 is piloted. The upper portion of this member is constituted by a kelly 13 having an upper threaded pin 14 screwed into a sub 15, which may form the lowermost portion of the drill pipe B. The drill stem member 13 itself is slidably splined in the upper portion of the body, as by forming the exterior 16 of the kelly of hexagonal shape (Fig. 6), fitting within a corresponding hexagonal socket 17 in the body. The drill stem member is provided with an external flange. 18 fitting within the body, and serving the purpose of holding the drill stem member within the body. After the drill stem member 13 has been placed-into the upper end of the body 11, a retainer ring 19 may be disposed over the member above its flange 18 and secured to the upper end of the body, as by use of Welding material 20, in order to prevent upward withdrawal of the kelly 13 from the body 11.

The body has a plurality of depending leg portions 11a defining longitudinal transverse body slots 21, in which cutter supporting members 22, 22a, 22b are disposed. These cutter supporting members are preferably equiangularly spaced around the bit axis and have their upper ends mounted on pivot or hinge pins 23 extending across the body slots 21 and suitably secured to the body, as by the use of welding material 24. The cutter supporting legs 22, 22a, 22b depend from their hinge pins 23, 23a, 23b to a substantial extent. They each have a bearing supporting pin 25 at the lower end, on which a roller side cutter 10, 10a or 10b is rotatably mounted. Anti-friction roller and ball bearing elements 26, 27 are disposed between each bearing supporting pin 25 and cutter 10, 10a or 10b, to reduce the friction therebetween. The ball bearing elements 27 also serve to retain the cutter on the bearing supporting pin.

The balls 27 may be inserted between each cutter 10, 10a, or 10b and its associated pin 25 through a passage 28 in the latter, which is closed by a suitable plug 29 welded, or otherwise suitably secured, to the pin.

The bearing supporting members 22, 22a, 22b, and their cutters 10, 10a, 10b, may occupy retracted positions substantially entirely within the confines of the main bit body 11, or they may be expanded outwardly of the body to a larger effective diameter than the inside diameter of a casing string (not shown) through 3 which the bit is moved, for the purpose of enlarging the well' bore below the casing shoe (not shown). In expanding the cutters 1i 10a, 10b, their supporting legs 22, 22a, 2212 are swung outwardly about the hinge pins 23, 23a, 23b to a predetermined extent.

The device for holding-the cutters expanded includes; a lower tubular member 30, which actually forms part. of the mandrel 12, and which ispiloted within a lower socket 3-1. in the kelly 13. The kelly 13 and lower tubular member 30 are assembled together for joint longitudinal movement by a swivel connection 32, which enables the lower tubular member to move angularl-y with. respect to the upper kelly. Such swivel connection may include ball bearing elements 33 mounted in a raceway 34 formed: on an. enlarged portion 35 of: the'lower. member 30,. the ball bearing elements also being; rollable inv aninternal race-- way 36 formed in the kelly itself. The balls may be inserted in. place through a passage: 37' extending: through the kelly flange 18. After the required number of balls have been mounted in the raceways; 34, 36, they are. held in assembled position by a plug 38 in the passageway 37, which is prevented from inadvertent outward movement from the passageway by engaging the main bit body 11.

The lower tubular member 30 depends from its boss. portion 35 through a guide and. thrust member 3.9, which rests upona shoulder 4.9-formed on the body.. This thrust member initially is disposed below the lower: end of the kelly 13; so as to allow the kelly 13 and tubular member 30. to be moved downwardly, for the purpose of holding the cutters 10, 10a, 19b and their supporting members 22, 22a, 22b in. an outward position, resisting inward movement of. the cutters from their outward position, and, under some conditions, actually shifting the cutters to their outwardly expanded position. The lower end of the mandrel member 30' is slidable in. a. lower guide 41 integral with the body 11, and forming a support for the mandrel to resist its. lateral movement.

The cutter supporting. members or legs 22', 22a, 22b and the cutters carried thereby may be expanded outwardly by a compressed helical expander spring 50 en? compassing the tubular member 30 and bearing upon an upper spring seat 51 attached to the body 11 immediately below the guidemember 39. The lower end of the spring bears upon an upper thrust block 52 that has a pin. 53 carrying the upper end of a link or connecting rod 54, whose lower end is pivota-lly mounted on a pinSSsuitably secured to the cutter supporting leg 22.

The upper spring seat 51 is in the form of an annular member having an external circumferential groove 5111 that may be disposed opposite a plurality of holes 51b extending'through the body. The outer ends 510 of these holes are cou-nterbored and threaded to receive the threaded portions of set screws 51a; whose inner shank portions Sle extend through the holes and intothe seat groove 51a.

In assembling the spring 50 in appropriate position between its upper seat 51 and the upper thrust block 52, the tubular mandrel 12.istelescoped into the body until the lower end'13a of the kelly engages the guide member 39, which bears upon the upper spring seat 51. The tubular member is forced inwardly of the body 11 to force the guide member 39 and spring seat 51 downwardly to compress the spring 50, as limited by engagement of the guide member 39 with the body portion at the lower end of the hexagonal socket 17. When the guide member 39 engages the body, the circumferential groove 51a of the spring seat is disposed opposite the lateral holes. 51b, whereupon the set screws Site may be threaded in the holes, their inner tapered ends 517" engaging the lower side of the circumferential groove 51a tof'orce the spring seat 51 slightly downwardly away from the thrust member 39. The ends 51f of the set screws remain in the groove 51a, to hold the spring seat 1 in appropriate position within the body.

Slidable on the mandrel 30' below the upper thrust block 52 is an intermediate thrust block 52a having a pin 53a on which the upper end of a thrust link or connecting rod 54a is pivoted, the lower end of this link being pivoted on a pin 55a secured to another one of the cutter supporting members or legs 22a. Yet another or lower thrust block 52b is slidable on the mandrel below the intermediate thrust block 52:: and carries the pin 53b on which the upper end of a lowermost link 54b is-pivotally mounted, the lower end of this link being pivoted on a pin 55b secured to. still a third cutter supporting member or leg 22b.

As illustrated, the upper, intermediate and lower thrust blocks 52, 52a, 52b are slidable on a. reduced diameter lower portion 30:: of the tubular member 30, the upper thrust block 52 being initially disposed adjacent a mandrel shoulder 30b, which may engage the upper portion of the upper thrust block.

One; manner of expanding, the cutters outwardly is to allow the compressed spring 50 to expand, which will shift the upper thrust block 52 downwardly on the mandrel 30, and, through the agency of the link 54', urge the cutter supporting leg 22 and the. cutter 10. outwardly. The upper thrust block 5.2 will move downwardly under the influence of the spring 5.0. until. it engages the intermediate. thrust block 52a, the. spring then moving both the upper and intermediate blocks 52, 52a downwardly as a unit to urge the cutter supporting legs 22 and. 22a outwardly. Thereafter, as the spring 50 continues to expand, the intermediate thrust block 52a engages the lower thrust block 52b, the three; blocks 52, 52a, 52b moving downwardly as a unit to urge all three of the cutter supporting legs 22, 22a, 22b and their associated cutters 10, 10a, 10b outwardly, through the agency of the intermediate. connecting rods 54, 54a, 54b. The extent. of expansion is limited by engagement of the. lower thrust block 52b with thelower body guide 41.

The spring 50 can be effective to urge the cutters out Wardly in the event it is desired to begin enlarging. the well bore below the well casing at a point above the bottom of the hole. If desired, the tubular mandrel. 30 can be. employed, in the absence of the expander spring 50,.

or to supplement the expander spring, in urging the cut ters 10,. 10a, 10b outwardly, particularly if downward movement of the body 11 can be prevented or resisted by the bottom of the. well bore, as. upon resting of a pilot hit E on. the bottom. It is to be. noted that the driving mandrel 12 originally occupied an upper position with respect to the body 11.. Downward. movement of the mandrel by urging the drill pipe string'B downwardly will force the mandrel shoulder 30b against. the upper thrust block 52 and first urge. the cutter supporting leg 22 and its cutter 10 outwardly; As downward movement of the mandrel 12 within the body 11 continues, the. upper thrust block engages the intermediate block 5211,. to urge the second cutter supporting leg 22a and cutter 10a outwardly. Continued downward movement will then cause the intermediate block to engage the lowermost block 52b, for the purpose of urging the third cutter supporting leg 22b and cutter 10b outwardly. The extent of such urging will be determined by engagement of the lower end 13a of the kelly 13-with the upper thrust and guide washer 39.

The cutters 10, 10a, 10b may be locked in retracted position initially by a holding arrangement, with the expander spring 50 fully compressed, and with the driving mandrel I2 occupying an upward position within the body 11; so as to insure downward passage of the bit through the well casing, and to enable the bit to be moved to any desired point in the well bore below the casing shoe before the hole enlarging operation is commenced.

This holding device may include a holding plate or arm having a hole 61 receiving the lower end of the ball retaining plug 29 for the cutter 10 and supporting arm 22. The plate 60 will prevent outward expansion-of the cutter 10 until the former member is removed. holding the expander spring 50 in its highly compressed condition and preventing its expansion, for the purpose of urging the supporting member 22 and the cutter 10 outwardly. The spring 50 is initially tending to urge only the cutter supporting member 22 and its cutter 10 outwardly, in view of the force exerted by the spring upon the upper thrust block 52 and the link 54 interconnecting the latter to the supporting member 22. The other cutters 10a, 10b, and their respective supporting members 22a, 22b, do not have any force exerted upon them; so long as the holding arm 60 is in place. However, it is preferred to hold them positively in a retracted position during lowering of the apparatus through the well bore to the point at which the hole enlarging operation is to commence. Thus, the cutters 10a, 10b are held initially in retracted position by a metallic strap 60a, such as relatively thin box strapping, embracing their supporting members 22a, 22b and the body, as well as the supporting member 22.

Removal of the holding plate 60 may be effective hydraulically. A central rod 62 is secured to the plate and projects upwardly into the central passage 300 formed through the lower tubular member 30. A fluted head 63 at the upper end of the rod is freely slidable within the passage 30c, to enable fluid to flow upwardly through the tubular member passage and the kelly passage 13b and into the drill pipe string B. A ball 64 may also be disposed in the passage 30c, or may be dropped down the drill pipe B when the cutters are to be expanded, this ball having a diameter substantially equal to the diameter of the passage 300; so as to function as a piston and enable the fluid under pressure within the drill pipe B and drill bit to force the central rod 62 downwardly and remove the holding plate 60 from the plug element 29 of the supporting member 22. Such removal allows the spring 50 to expand, to bear upon the strap and break it; releasing the other supporting members 22a, 22b and their cutters 10a, 10b for lateral outward shifting. All of the cutters and their supporting members can now be expanded either by the expander spring 50, the driving mandrel 12, or both. If the spring 50 is incapable of breaking the strap 60a, rotation of the bit and rubbing of the strap upon the wall of the formation will produce its disruption. In this connection, disruption may be facilitated by providing a weakened section 60b in the stra V I? is desired to have each of the cutter members operate upon a particular annular portion of the formation shoulder. Thus, the cutter member 10 is to operate around the annular portion R of the shoulder (see Fig. the cutter member a is to operate upon the annular portion S of the shoulder; and the cutter member 10b is to operate upon the annular portion T of the shoulder. Inasmuch as these annular portions are disposed different lateral distances from the axis of the well bore, the cutters are to be expanded outwardly different amounts ,to locate each cutter at its proper position upon the formation shoulder C.

Since the cutter supporting leg 22 and its cutter 10 are to be swung outwardly from their fully retracted position to the greatest extent, the pin connection 55 between the connecting rod 54 and the cutter supporting leg 22 is disposed a lesser distance from the hinge pin 23 of the cutter supporting leg 22, than the distance from its hinge pm 23a of the pin connection 55a between the second cutter supporting leg 22a and its connecting rod 54a. Similarly, the distance from the hinge pin 23b for the cutter supporting leg 22b and its pin connection 55b with its connecting rod 54b is greater than the distance between the hinge pin of the second leg 22a and its pin connection 55a to its link or connecting rod 54a. Accordingly, for the same longitudinal movement, the upper thrust block 52 will swing its cutter supporting leg 22 a greater arcuate extent than the intermediate thrust block 5211 will swing its cutter supporting leg 22a, and this latter thrust block will, in turn, swing the cutter supporting leg 22a a greater arcuate distance than the lower thrust block 52b swing? the cutter supporting leg 22b. 7

Despite the fact that the lever arm distance of the pins 55, 55a, 55b connecting the rods 54, 54a, 54b to the cutter supporting members is different, it is desired to have the first cutter supporting leg 22 swing outwardly to a certain arcuate extent before the intermediate supporting leg 22a commences moving outwardly from its retracted position. Also, this intermediate leg 22a is to swing outwardly from its fully retracted position to a certain extent before the remaining leg 22b and its cutter 10b commences moving outwardly. To accomplish this purpose, the intermediate thrust block 52a is initially spaced downwardly from the upper thrust block by a certain distance; so that the upper thrust block 52 must move downwardly throughthis distance and swing its cutter supporting leg 22 and cutter 10 outwardly before the upper thrust block 52 engages the intermediate thrust block 52a, to commence outward swinging of the intermediate leg 22a and cutter 10a. Similarly, a longitudinal space exists initially between the intermediate and lower thrust blocks 52a, 52b, to require the intermediate thrust block 52a to swing the intermediate cutter 10a outwardly to a certain arcuate extent before it engages the lower thrust block 52b and shifts the latter downwardly, to effect outward swinging of the cutter supporting leg 22b and cutter 10b.

Thus, the upper thrust block 52 will move downwardly to shift the cutter 10 outwardly, and while the drill string and bit is rotating, cause the cutter to start producing the formation shoulder C. After an inner portion of this formation shoulder, corresponding to the distance T in Fig. 5, is formed by the outward expansion of the cutter 10, the upper thrust block 52 will then engage the intermediate thrust block 52a and commence shifting the intermediate cutter 10a outwardly. The first cutter 10 has been expanded outwardly to a greater extent than the second cutter 10a and will remain in this advanced position during rotation of the drill bit, whereby the first cutter 10 enlarges the formation shoulder C to a still greater lateral extent, as by commencing to operate upon a formation shoulder portion corresponding to the distance S in Fig. 5. The second cutter 10a, during further outward swinging of the first cutter 10, will be disposed over the inner distance T of the formation shoulder. As the two thrust blocks 52, 52a move downwardly as a unit along the mandrel 30, to expand their cutters 10, 10a outwardly, the intermediate block engages the lower thrust block 52b and commences urging the remaining cutter supporting leg 22b and its cutter 10b outwardly. Inasmuch as all three thrust blocks are contacting one another, they will swing outwardly simultaneously, the first supporting member 22 and its cutter 10 leading the second supporting member 22a and its cutter 10a in lateral extent, and the second cutter supporting member and its cutter, in turn, leading the remaining supporting member 22b and its cutter 10b in lateral extent. The blocks all continue moving downwardly to their maximum extent, the first cutter 10 swingmg across the entire formation shoulder distance C, and finally being capable of rolling around the outermost annular portion R of the shoulder. The second cutter 10a 1s capable of rolling around the intermediate annular portion S of the shoulder, and the third cutter 10b is capable of rolling around the inner annular portion T of the shoulder.

In the event that the thrust blocks have been shifted downwardly by the spring 50, the production of the full shoulder C will enable theoperator to lower the drill pipe B slightly, to telescope the mandrel 12 within the body 11 until the lower end 13a of the kelly 13 engages the thrust washer 13a. The drilling weight can then be imposed directly through the kelly 13 onto the body 11, and through the hinge pins 23, 23a, 23b and supporting members 22, 22a, 22b to the cutters 10, 10a, 10b. At the same time, the mandrel shoulder 30b is disposed immediately adia'c'ent the upper thrust block 52', in order to hold all of the thrust blocks in their downward position and preclude the. reactive forces of the formation on the cutters from urging the latter inwardly to a position in which they would drill an undersized hole. In effect, the mandrel shoulder 30b locks or retains the cutters outwardly to their maximum expanded positions.

In order to stabilize the drill bit in the hole, decrease shocks that would otherwise be imposed thereon, and introduce a greater tendency to drill a concentric enlarged well bore, the cutters are longitudinally spaced with respect to each other; so as to have respective longitudinal wall portions of the well bore against which they can bear. A

longitudinal spacing can be obtained by making the cutter supporting leg 22a for the cutter 10a longer than the length of the supporting leg 22 for the cutter 1t and by making the cutter supporting leg 22b for the cutter 10b longer than the leg 22a.

Another mode of longitudinally spacing the cutters with respect to each other is to dispose the hinge pin 23a for the cutter 10a lower than the hinge pin 23 for the cutter l0, and by disposing the hinge pin 23b for the cutter 1% lower than the hinge pin 23a. Although either of the above arrangements can be used to obtain longitudinal spacing of the cutters, both arrangements can also be employed', which is done in the present case. Thus, the lower disposition of the hinge pin 23a and the greater length of its associated supporting arm 22a places the cutter 19a lower than the cutter 10; whereas, the still lower disposition of the hinge pin 23b and the greater length of the supporting leg 22b places the cutter 1% lower than the cutter 16a, as clearly illustrated in Fig. 5.

The cutter 10 operates upon the outermost formation shoulder R, its back tooth portions bearing upon the outermost wall H of the enlarged well bore. The cutter 10a operates upon a lower and intermediate formation shoulder portion S, with the back faces of its cutter teeth engaging the longitudinally extending intermediate wall F of the well bore. Again, the cutter 10b is disposed in a still lower position, operating upon the inner formation shoulder portion T and with the back faces of its cutter teeth engaging the inner enlarged longitudinal formation wall G.

In view of the stepped arrangement of the cutters and their engagement with their associated formation walls, the drill bit has greater stability during its hole enlarging operation, in view of the resistance provided by the formation walls H, F, G against the back faces of the cutters. There is less tendency for the drill bit to wobble in the well bore, which results in a greater tendency for the bit to drill an enlarged hole which is concentric to the axis of the well bore previously produced. In addition, the greater stability of the operation of the drill bit decreases any'shock loads that might otherwise be imposed upon it.

The longitudinal spacing of the cutters from each other has yet a further important advantage. Such spacing enables each cutter to be made of a much larger diameter and still be fully retractable within the confines of the body ll. If the cutters all were located in substantially the same cross-sectional plane, their diameter, or diameters, would be limited by the factor of interference with each other when in retracted position. With longitudinally spaced cutters, however, such interferonce is greatly minimized, if not eliminated entirely, each cutter being capable of spanning a greater chordal distance across the body when in retracted position, and, ifdesired, it can also be made of greater axial length so as. to have greater tooth lengths. It is apparent from the. drawings, and especially from Fig. 3, that the cutters do not: interfere with each other, because of their relative longitudinal spacing along the body 11.

The tool A is assembled with the parts occupying the positions illustrated. in Fig. 3, the holding plate 60 and band 6.9a securing. the cutters 10, 10a, 10b in retracted position;. with the. spring 50. (when a spring is-used) undermaxim-um compression. The tubular mandrel 11 is disposed upwardly with respect to the body it, as limited by engagement of the Kelly-flange 1'8 with the retainer ring 19-. The bit is attached to the drill pipe B and lowered in the well bore.

When the location in the bore hole below the cas-' exit from the lower end of the passage into the well bore,

for the purpose of cleaning the cutters and washing the cuttings upwardly to the top' of the well bore.

After the holding device hasbcen' removed, the spring can expand to exert its force upon the band a to break itand release allof the legs 22, 22a, 22b and their associated cutters. This expanding action first urgesthe upper block 52 downwardly, and, through the thrust link 54, swings the first cutter 1'0 outwardly, forcing the cutter 10' against the wall of the formation. The drill pipe and the rotarydrill bit are then rotated at the proper speed, without imposing drilling weight on the pipe and bit, the single cutter 10 digging into the wall of the formation and commencingt-he enlargement of the inner distance T of the stepped shoulder C therein under the influence of the spring- 50. As the spring expends, as a result of outward movement of the first cutter 10-, the upper block 52 moves down until it engages the intermediate thrust block 52a, which then urges the second cutter supporting member 22a and cutter 10a outwardly. The spring 50 continues its expansion, simul taneously shifting the first and second cutter supporting members 22, 2-21 andtheir associated cutters 10, 10a outwardly, the first cutter 10 leading the second cutter 10a and continuing to enlarge the lateral extent of the stepped format-ion shoulder, commencing the production of the intermediate distance- S of the shoulder during rotation of the drill bit.

As the two cutters continue their outward movement,

as a-resul t of expansion'of the spring and downward movement of' the upper and intermediate thrust blocks, the intermediate block 52a finally engages the lower thrust block 521;; which is urged downwardly to swing the third cutter supporting member 22b and cutter 10b outwardly. Rotation of the drill bit is continued, the spring Sil shifting allthree blocks downwardly together and urging the cutters outwardly, the first cutter producing the outermost portion R of the shoulder. When the lower block 525 engages the lower body guide 41, the cutters l t 1 0a, 1912' are precluded from swinging outwardly to any further extent, but they are then 10- cated with the outermost cutter 10 disposed upon the outermost portion R of the shoulder, the intermediate cutter 10a on the lower, intermediate portion S of the shoulder, and the innermost cutter 10b upon the still lower, innermost portion 1* of the shoulder. The annu lar paths R, S, T traced. by the cutters upon the formation shoulder C during rotation of the bitpreferably overlap one another to: a slight extent; to insure that the cutter teeth will operate upon allportions of the stepped formation shoulder;

After-the stepped formationshoulder C has been produced, down weight or drilling weight may be imposed on the drilling string B, which will telescopethe mandrel 12 in the body 11 and shift the. lower end 13a of'the kelly- 13- into engagement with the thrust washer 39,

the drilling weight then being transmitted directly through the body' 11 to the cutter supporting members 22, 22a, 22b and the cutters 10 10a, 10b. During the imposition of the drilling weight, the bit is rotated at the proper speed, the-cuttersoperating-upon their individual and longitudinally spaced annular portions of the shoulder to remove the formation material in a downward direction, effecting the hole enlarging to the desired greatly increased diameter. As mentioned above, the downward telescoping of the driving mandrel 12 in the body 11 also locates the mandrel shoulder 30b immediately adjacent the upper thrust block 52, to prevent any substantial retraction of the cutters from their maximum expanded positions.

When the Well bore has been enlarged to the desired length, or upon the cutters becoming dull, the entire tool may be removed from the well bore merely by elevating the drill string B. Such elevating movement will lift the driving mandrel 12 within the main bit body 11 and will raise the mandrel shoulder 30b above the upper thrust block 52. As the tool passes into an upper lesser diameter portion of the well bore, or into the well casing, the walls of the casing or well bore will engage the cutter supporting legs 22, 22a, 22b, and force them inwardly against the action of the expander spring 50. The cutter supporting members will ride the wall of the casing during removal of the bit to the top of the well bore.

As indicated above, if the pilot bit E is resting upon the bottom of the well bore, the spring 50 need not be used, expansion occurring as a result of shifting the driving mandrel 12 downwardly within the body 11, to positively force the thrust blocks 52, 52a, 52b downwardly and the cutter supporting legs and cutters outwardly in the above-noted sequence, in order to produce the stepped formation shoulder C. The extent of downward movement of the mandrel 12, and of outward expansion of the cutters, is limited by engagement of the lower end 13a of the kelly 13 with the thrust and guide washer 39.

It is, accordingly, apparent that an expansible drill bit has been provided which is capable of increasing the well bore diameter considerably. A stepped formation shoulder of substantially great lateral extent is first formed, and each cutter is caused to operate upon its individual portion of this shoulder; so that each cutter, in effect, constitutes an individual bit capable of enlarging the well bore from one diameter to another diameter. Thus, the innermost cutter b will enlarge the hole by the radius T, the next, or intermediate, cutter 10a will increase the size of the enlarged hole by the additional radius S, and the outer cutter 10 will further increase the size of the hole by the additional radius R. The cutters, collectively, progressively increase the bore hole diameter, and achieve the same purpose as if individual bits were run in the hole, one bit increasing the well bore size by the radius T, another bit then being run in the hole to further increase the hole size by the radius S, and still another bit being thereafter run I in the hole to further increase the size of the bore by the radius R. By virtue of the present invention, a single bit achieves the same result as the plurality of bits, with a single run of the equipment in the bore hole. In addition, the ability to use roller cutters allows the bit to operate effectively in comparatively hard formations, and to increase the bore hole size in such formations considerably. Each cutter engages its own formation wall, and, because of the circumferential spacing of the cutters from each other, tend to maintain each other in their proper paths on the stepped formation shoulder concentrically of the well bore axis.

The inventor claims:

1. In an expansible drill bit: a body; a plurality of individual cutter means mounted on said body for lateral movement with respect to said body and each cutter means initially occupying a retracted position on said body; one of said cutter means extending along said body substantially lower than another of said cutter means; and means for shifting said individual cutter means laterally outward, said shifting means including instrumentalities movable with respect to said body and engageable with all of said individual cutter means for shifting said lower cutter means laterally from its initially retracted position to a lesser maximum extent than said another of said cutter means to place said lower cutter means a lesser maximum distance from the axis of said body than said another of said individual cutter means to cause said lower cutter means to form and operate upon a transverse formation shoulder disposed within and lower than the transverse formation shoulder formed and operated upon by said another of said individual cutter means.

2. In an expansible drill bit: a body; a plurality of individual cutter means mounted on said body for lateral movement with respect to said body and each cutter means initially occupying a retracted position on said body; said individual cutter meansbeing circumferentially disposed around said body with one of said cutter means located substantially lower along said body than another of said cutter means; means engageable with said individual cutter means and movable with respect to said body for shifting said lower individual cutter means laterally outward from its initially retracted position to a lesser maximum extent than another individual cutter means located in a higher position along said body to place said lower cutter means a lesser maximum distance from the axis of said body than said higher cutter means to cause said lower cutter means to form and operate upon a transverse formation shoulder disposed within and lower than the transverse formation shoulder formed and operated upon by said higher cutter means; and stop means for limiting the extent of outward expansion of all of said individual cutter means.

3. In an expansible drill bit: a body; a plurality of supporting members disposed circumferentially around said body; a cutter mounted on each of said supporting members; means mounting said supporting members on said body for lateral movement with respect to said body; one of said supporting members being substantially longer than another of said supporting members so as to dispose the cutter on said one of said supporting members substantially lower along said body than the cutter on said another of said supporting members; and means engageable with said supporting members and movable with respect to said body for shifting said supporting members laterally of said body to shift said longer supporting member a lesser maximum lateral distance from the axis of said body than said another of said supporting members to place said lower cutter a lesser maximum distance from the axis of said'body than said cutter on said another of said supporting members, to cause said lower cutter to form and operate upon a transverse formation shoulder disposed within and lower than the transverse formation shoulder formed and operated upon by said cutter on said another of said supporting members.

4. In an expansible drill bit: a body; a plurality of supporting members disposed circumferentially around said body; a cutter mounted on each of said supporting members; means mounting said supporting members on said body for lateral movement with respect to said body, said mounting means including instrumentalities mounting one of said supporting members at a substantially lower position on said body than another of said supporting members to dispose the cutter on said one of said supporting members at a substantially lower position along said body than the cutter on said another of said supporting members; and means engageable with said supporting members and movable with respect to said body for shifting said supporting members laterally of said body to shift said lower cutter a lesser maximum lateral distance from the axis of said body than another cutter to place said lower cutter a lesser maximum distance from the axis of said body than said another cutter to cause said lower cutter to form and operate upon a transverse formation shoulder disposed within and lower than the transverse formation shoulder formed and operated upon by said another cutter.

5. In an expansible drill bit: a body; a plurality of sup- 11 port-ing members disposed circumferentially around said body; a cutter mounted on each of said supporting members; means mounting said supporting members on said body for lateral movement with respect to said body, said mounting means including instrumentalities: mounting one of said supporting members at a substantially lower position on said body than: another of said supporting members to dispose the cutter on said one of said supporting members at a substantally lower position along said body than the, cutter on said another of said supporting members; said one of said supporting members being longer than said another of said supporting members; and means engageable with said supporting members and movable with respect to said body for-shiftin-g'said supporting members laterally of said' body to shift the cutter'on said one of said supporting members a lesser maximum lateral: distance from the axis ofsaid body than the cutter on said another of said supporting members toplace said lower cutter a lesser maximum distance from the axis of said: body than said cutter on said another of said supporting members, to cause said lower cutter to form: and oper-- ate upon a transverse formation shoulder disposed within. and: lower than the transverse formation shoulder formed: and operated: upon by said cutter on said? another of said supporting members.

6. In. an. expansibledrill bit: a body; a. plurality of sup porting members disposed circumferentially around: said body; a cutter mounted oneach. of said supportingmembers; means pivotally mounting said supporting members on said body for lateral movement with respectto. said body; the pivotal axis of one of said supporting members being disposed substantially lower on. said body than the. pivotal axis of another of said supporting; members.

to dispose the cutter on said one of said supportingmernbers substantially lower along said body than the cutter on said another of said supporting members; and means engageable with. said supporting members and movable; with respect to said-body for shifting said supporting members laterally of said body to shift said cutter on said one of said supporting members a lesser maximum lateral distance from the axis of said body than the; cutter on. said another of said supporting members to place said lower cutter a lesser maximum distance from the axis:

of said body than: said cutter on said another of said supporting members, to cause said lower cutter to form and operate upon: a transverse formation shoulder disposed withinand lower than the transverse formation. shoulder formed and operated uponby said cutter on said another of said supporting members.

7. In an expansible drill bit? a body; a. plurality of supporting members disposed circumferentially around said body; a cutter mounted on; each of: said supporting members; meauspi otally mounting said supporting members on said body for lateral movement with respect to said body; one of said. supporting members being-substantially longer than. another of said supporting members to dispose the cutter on said; one of said supporting: members substantially lower along said body than the cutter on an.- other of said supporting members; and: means engageable with. said supporting members and movable with respectto said body for shifting said supporting members laterally of? said body to shift saidlowen cutter a lesser maxilateral distance from they axis of said body than an.- other cutter to place said lower cutter a lesser maximum; distance from the axis of said body-than said another cutter to cause said lower cutter to form and operate-upon: a transverse formation shoulder disposed within and lower than the; transverse. formation shoulder formed andioperated upon; by said another cutter.

8. In an expansible drill bit: a body; a plurality of supporting members disposed circumferentially around said body; a. cutter mounted on; each of said supporting meme bers; means pivotally mounting said supporting members.

on said body for lateral movement with respect to said body; one of said supporting members being substantially longer than another of said supporting members, said 12 oneof said supporting members having its pivotal axis substantially lower than the pivotal axis of said another of said supporting members, to dispose the cutter on said one of'said supporting members substantially lower than the cutter on said another of said supporting members; and means engageable with said supporting members and movable with respect tosaid body for shifting said supporting members laterally of said body to shift said lower cutter a lesser maximum lateral distance from the axis of said body than another cutter to place said lower cutter a lesser maximum distance from the axis of said body than said another cutter to cause said lower cutter to form and operate upon a transverse formation shoulder disposed within andlower than the transverse formation shoulder formed and operated upon by said another cutmovable with respect to said body for shifting said supporting members laterally of said body to shift one of said cutters a greater; maximum lateral distance from the axis of said body than another cutter; latch means secured to said higher supporting member only for holding said higher supporting member inretracted position; and a readily breakable member surrounding said supporting members to hold said another of said supporting members in retracted position.

10. In an expansibledrillbit: a body; a plurality of supporting members disposed circumferentially around said body; oneof said supporting members being disposed higher along said body than another of said supporting members; a cutter mounted on each of said supporting members; means mounting said supporting members on said body for lateral movement with respect to saidbody; spring means engageablewith said supporting members and movable with respect to said body for shifting said supporting members l'aterallyof saidbody to shift one of said cutters a greater lateral maximum distance from the axis of said body than another cutter; latch means secured to said higher supporting member only to prevent expansion of said spring means and tohold said higher supporting member in retracted position; andmeans encompassing all ofsaid supporting members to hold said an other ofsaid supporting members in retracted position.

1-1. In an expansible drillbit: a body; a plurality of individual cutter means-mounted on saidbody for lateral movement with respect to said body; means for shifting said individual cutter means laterally outward, including a stressedspring', a spring seat disposed above said springand against which said spring bears, said spring seat hav-- ing a peripheral groove therein; and pins extending genorally radially through said body and into said groove tosecure saidspring seatto said body.

12. In an expansible drillbit: a body; aplurality of individual cutter means mounted on said body for lateral movement with respect to said body; means for shifting said individual cutter means laterally outward, including a stressed spring; a spring seat disposed above said spring and against which said spring bears, said spring seat'having a peripheral groove therein; and elements threaded generally radially into said body and having tapered ends adapted to be guided into and disposed within said groove to secure said spring seat to said body.

13. In an expansible drill bit: a body; a plurality of supporting members disposed circumferentially around said body; a; cutter mounted on each of said supporting members; means mounting said supporting members on saidbodyfor lateralmovement'with respect to-said-body; means includinga spring for shifting said supporting:

members laterally of said body; means connectible to a drill string and slidably splined to said body for holding said supporting members outwardly of said body; a movable guide element engageable by said connectible means to limit longitudinal movement of said connectible means with respect to said body in one direction; a spring seat engageable with said spring and guide element and movable longitudinally of said body by said connectible means and guide element to compress said spring; and means extending laterally through said body and engaging said spring seat to secure said spring seat to said body.

14. In an expansible drill bit: a body; a plurality of supporting members disposed circumferentially around said body; a cutter mounted on each of said supporting members; means mounting said supporting members on said body for lateral movement with respect to said body; means including a spring for shifting said supporting members laterally of said body; means connectible to a drill string and slidably splined to said body for holding said supporting members outwardly of said body; a movable guide element engageable by said connectible means to limit longitudinal movement of said connectible means with respect to said body in one direction; a spring seat engageable with said spring and guide element and movable longitudinally of said body by said connectible means and guide element to compress said spring, said spring seat having a circumferential groove; and elements threaded into said body and disposed in said groove to retain said spring seat in said body.

15. In an expansible drill bit: a body; a plurality of supporting members disposed circumferentially around said body; a conical cutter mounted on each of said supporting members for rotation on said supporting member about an axis inclined inwardly and downwardly and to form a transverse shoulder in the formation of a bore hole in which the drill bit is disposed; means mounting said supporting members on said body for lateral movement with respect to said body; one of said supporting members being substantially longer than another of said supporting members so as to dispose the cutter on said one of said supporting members substantially lower along said body than the cutter on said another of said supporting members; and means engageable with said supporting members and movable with respect to said body for shifting said longer supporting member laterally alesser distance than said another supporting member to cause said cutter on said longer supporting member to form and operate upon a transverse formation shoulder disposed within and lower than the transverse formation shoulder formed and operated upon by said cutter on said another supporting member.

16. In an expansible drill bit: a body; a plurality of supporting members disposed circumferentially around said body; a conical cutter mounted on each of said supporting members for rotation on said supporting member about an axis inclined inwardly and downwardly and to form a transverse shoulder in the formation of a bore hole in which the drill bit is disposed; means mounting said supporting members on said body for lateral movement with respect to said body; one of said supporting members and the cutter mounted thereon being disposed along said body substantially lower than another of said supporting members and the cutter mounted thereon; and

means engageable with said supporting members and movable with respect to said body for shifting said lower supporting member and its cutter laterally a lesser distance than said other of said supporting members and its cutter to cause said cutter on said lower supporting member to form and operate upon a transverse formation shoulder disposed within and lower than the transverse formation shoulder formed and operated upon by said cutter on said other supporting member.

References Cited in the file of this patent UNITED STATES PATENTS Kammerer Oct. 6, 

